PASCO ME-9837 User manual

Instruction Manual

Manual No. 012-08862

Discover Centripetal

Force Kit

Model No. ME-9837

2®

Table of Contents

Equipment List........................................................... 3

Introduction ............................................................. 4

Equipment Setup ........................................................ 5

The Classic Centripetal Force Lab ..................................... 6

Velocity versus Force ................................................... 8

Velocity versus Mass ................................................... 9

Velocity versus Radius .................................................10

Questions ...............................................................11

Demonstrations .........................................................11

Appendix A: Technical Support .......................................12

Appendix B: Copyright and Warranty Information .................. 12

Model No. ME-9837 Discover Centripetal Force Kit

Discover Centripetal Force Kit

Model No. ME-9837

Equipment List

Included Equipment Replacement

Model Number

1. Rubber stoppers

(sizes: 6, 8, 10, 11.5, and 13)

2. Hollow tube (2)

3. Plastic ties (10)

4. Yellow string (73 m) ME-9876

Additional Equipment Recommended

Safety goggles

Marking pen

Force Sensor CI-6746 or PS-2104

Hooked Mass Set SE-8759

Newton Spring Scale (20N) SE-8718

1 (#6)

1 (#8)

1 (#10)

1 (#11.5)

1 (#13)

* Please contact PASCO Technical Support when no replacement part number is provided.

Discover Centripetal Force Kit Model No. ME-9837

4®

Introduction

The Discover Centripetal Force Kit contains the materials necessary to

perform the classical centripetal force lab similar to the first example

listed in the table below. In addition, the Discover Centripetal Force

Kit can be used in conjunction with Force Sensors or Newton Spring

Scales.

Centripetal Force is an often misunderstood physical concept. Among

other things, the popular, yet, misused word "centrifugal" contributes

to students' misconceptions. An object moving in uniform circular

motion experiences a net inward-pointing force, called the centripetal

force. It is important for students to identify the agent for each force

that contributes to the centripetal force (net force) for an object moving

in uniform circular motion.

The table below gives examples of the centripetal force for certain

occurrences:

Included with the Discover Centripetal Force Kit are rubber stoppers

of widely varying masses. Convenient blue ties are provided to attach

the stoppers easily to the bright, sturdy string. In addition, (2) two

tubes are included to use for multiple lab groups. The tubes are

chamfered to decrease friction on the string.

Situation Centripetal Force

An object twirled in a horizontal

circle. Tension from the string.

Car driving in a circle. Static friction on the tires directed

toward the center.

A satellite. Force due to gravity.

A “centrifuge.” The normal force from the wall of the

“centrifuge.”

Model No. ME-9837 Discover Centripetal Force Kit

Equipment Setup

1. Cut a piece of string approximately 1 meter long and feed it through

the hollow tube.

2. Secure a plastic tie through the center hole in each stopper.

3. Tie one end of the string to the plastic tie to the stopper that is to be

used in the specific experiment.

4. Tie a loop at the other end of the string and hook a mass through the

loop.

Important! Please follow these SAFETY guidelines:

•Put on safety goggles!

•Make sure that no one is standing close to avoid hitting others!

•Hold the tube far enough away to avoid hitting self.

5. Firmly hold the tube and start rotating (spinning) the rubber stopper

as shown in the following photo (starting rotation). Continue

spinning the stopper until it reaches full rotation.

hollow tube

stopper

hooked mass

string (1m)

loop in string

plastic tie

Discover Centripetal Force Kit Model No. ME-9837

6®

Labs with the Discover

Centripetal Force Kit

The Classical Centripetal Force Lab

Set up the lab as shown in the general setup section.

Overview

In this lab, the dependent variable is always the linear velocity (v). The

independent variables are the radius (r), the hanging weight -

determined by the hanging mass (mh) - and the spinning mass (ms).

When the velocity is plotted as a function of one of the independent

variables, the other two independent variables must be kept constant.

It is important, therefore, to keep track of these values using the

following data table for each of the 3 sections of this lab:

Spinning mass:

starting rotation Spinning mass:

full rotation

Model No. ME-9837 Discover Centripetal Force Kit

For each data point collected, students must:

• Select and mark a predetermined radius.

• Select and attach predetermined hanging and swinging masses.

• Adjust the "swing speed" until the predetermined radius is attained.

• Time ten (10) full rotations.

Calculate the Linear Velocity

To determine the linear velocity of the spinning mass, measure the

period (T) and the radius (r). To find the period, divide the time of the

10 full rotations by 10. To calculate the linear velocity (v) use the

following equation:

In order to maintain a constant radius, mark the string with a pen.

Practice spinning the mass and observing the mark on the string.

Calculate the Force

The centripetal force on the spinning mass is roughly equal to the

weight of the hanging mass. Measure the hanging mass and use this

value to calculate the centripetal force.

radius (m) mh(kg) ms(kg) V (m/s)

ν2πr

---------=

Discover Centripetal Force Kit Model No. ME-9837

8®

Velocity versus Force

While using the same spinning mass and maintaining the same radius,

students find the corresponding velocities for different hanging

masses. A graph of Force versus Velocity should yield a square root

graph and a relationship of

where k1is a constant.

Sample Data:

The following data is for a spinning mass of 22 g (#6 stopper) and a

radius of 0.5 m.

νk1F=

radius (m) mh(kg) ms(kg) V (m/s)

.5 .1 .022 4.4

.5 .2 .022 6.3

.5 .3 .022 8.0

.5 .4 .022 9.2

.5 .5 .022 10.2

Model No. ME-9837 Discover Centripetal Force Kit

Velocity versus Mass

While maintaining the same hanging mass and radius, students find the

corresponding velocity for different spinning masses. A graph of

Velocity versus Msshould yield a graph with the relationship of

where k2is a constant.

Sample Data:

The following data is for a hanging mass of 500 g and a radius of

0.5 m.

νk2

------=

radius (m) mh(kg) ms(kg) V (m/s)

.5 .5 .022 10.0

.5 .5 .034 8.2

.5 .5 .056 6.4

.5 .5 .086 5.2

.5 .5 .109 4.5

Discover Centripetal Force Kit Model No. ME-9837

10 ®

Velocity versus Radius

While maintaining the same hanging mass and spinning mass, students

find the corresponding velocity for different radii. A graph of Velocity

versus Radius should yield a graph with a relationship of

where k3is a constant.

Sample Data:

The following data is for a hanging mass of 500 g and a spinning mass

of 56 g (#10 stopper).

νk3r=

radius (m) mh(kg) ms(kg) V (m/s)

.2 .5 .056 3.8

.3 .5 .056 4.9

.4 .5 .056 5.8

.5 .5 .056 6.5

.6 .5 .056 7.1

.8 .5 .056 8.2

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